1. Field of the Invention
The present invention relates to an image forming apparatus in which a reading unit is closably attached to an upper portion of a recording unit and which has a scanner function, a printer function, a copying function, or the like.
2. Description of the Related Art
Among image forming apparatuses each having a recording unit for forming an image onto a sheet and a reading unit for reading an original, there is an image forming apparatus with a construction in which the reading unit is closably attached to the recording unit. According to such a construction, by opening the reading unit, an access to a discharge tray just under the reading unit or an access into the recording unit for the purpose of executing a jam process or a maintenance operation can be easily performed.
Japanese Patent Application Laid-Open No. 2007-010949 discloses an apparatus in which a pair of stays are rotatably supported to both sides of an upper portion of a recording unit and the other edge of each stay is slidably connected along a guide groove formed in a reading unit. The stay is urged by a spring in such a direction as to open the reading unit. A moment in such a direction as to open the reading unit acts on the reading unit by the urging force even in consideration of a moment that is caused by a weight of the reading unit itself and the reading unit is held in its opening state, thereby avoiding a drop shock and preventing a finger of the operator from being nipped when the reading unit is closed.
However, a relatively strong spring force is necessary in order to hold the reading unit in its opening state. In a state where the reading unit was closed, the spring has further been charged and locked. In order to prevent a creep due to the spring force, it is necessary that ambient parts are formed in rigid shapes and are made of a strong material. A structure is also complicated. Due to those reasons, a size and costs of the apparatus are increased.
Japanese Patent Application Laid-Open No. 2006-184530 discloses an image forming apparatus in which a stay is rotatably supported to a recording unit and a projection provided for a reading unit is slidably connected along a guide groove formed in the stay. According to the apparatus, the guide groove formed in the stay is formed by a ring-shaped groove having: a first groove along which the projection slides when the reading unit is opened; and a second groove along which the projecting portion slides when the reading unit is closed. The apparatus is constructed in such a manner that the projection of the stay is circulated once along the guide groove by the one opening/closing operation. A stay position control spring for preventing a backward-running or an ahead-running of the stay and the like are also provided. The second groove is narrower than the projection. When the projection moves in the second groove, the projection is flexuously deformed, thereby preventing the drop shock, finger-nipping of the operator, or the like when the reading unit is closed. If the reading unit is slightly closed after the reading unit was opened to a full-open state from the closed state, the reading unit can be held in the opening state. When the reading unit is opened to the full-open state again, the reading unit can be closed.
However, since the ring-shaped guide groove constructed by the two different paths at the time when the reading unit is opened and when it is closed is necessary, a space efficiency is low and an enlargement in size of the apparatus is caused. In such an apparatus, by arranging the guide groove near an opening/closing axis of the reading unit, the ring-shaped guide groove can be miniaturized. However, when the reading unit is held at the opening position, since a load caused by an external force increases depending on leverage, it is necessary to take such a countermeasure that a strong material adapted to endure the unprepared operation of the operator is used or the like, resulting in an increase in costs. Since the backward-running or the ahead-running of the stay is prevented by the position control, there is also a case where even if the external force which is applied to the stay is very small, the backward-running or the ahead-running occurs and the opening/closing operation of the reading unit becomes unstable.
The invention is made in consideration of such a technical problem. It is an object of the invention to provide an image forming apparatus in which a reading unit is closably constructed for a recording unit, wherein an opening/closing operability of the reading unit can be improved without enlarging a size of apparatus.